sfc: Hold efx_nic::stats_lock while reading efx_nic::mac_stats
efx_nic::stats_lock is used to serialise stats updates, but each
reader was dropping it before it finished reading efx_nic::mac_stats.
If there were concurrent stats reads using procfs, or one using procfs
and one using ethtool, an update could race with a read. On a 32-bit
system, the reader could see word-tearing of 64-bit stats (32 bits of
the old value and 32 bits of the new).
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 9353ce8..b604014 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -704,6 +704,7 @@
* can provide. Generic code converts these into a standard
* &struct net_device_stats.
* @stats_lock: Statistics update lock. Serialises statistics fetches
+ * and access to @mac_stats.
*
* This is stored in the private area of the &struct net_device.
*/